The present invention relates generally to fluid machines, and more particularly to an improved fluid machine and to a power tool driven by the same.
Rotary fluid machines of the sliding vane type are already known. They have two components one of which is eccentrically received within the other and one of which rotates with reference to the other. One of the components is formed with radial slots in which the vanes are slidably accommodated to engage the other component during the relative rotation. If the inner component is rotated, the vanes are urged outwardly into engagement with the inner surface bounding the cavity in the outer component by centrifugal force, and also in most instances by compressed air and/or springs which act upon the vanes. If the outer component rotates, centrifugal action is eliminated as a factor, but compressed air and/or springs are used.
Springs are used in the type of fluid motor having a rotatable inner component, only if the motor is to start immediately upon the application of pressure fluid without any slightest delay; they are not necessary for any other purposes. If the motor is of the type wherein the outer component rotates, however, the use of springs is of greater importance because no centrifugal force is available to urge the vanes into sealing engagement with the other component. This means that a uniform contact pressure of the vanes can then be obtained only by the use of springs, if it is desired that the contact pressure be independent of fluctuations in the pressurized air that is supplied.
Springs for biasing the vanes have been conceived as leaf springs and also as various steel wire springs of helical configuration. They all have the disadvantage that their deformation equals the total stroke of movement of each of the vanes, and that given the high number of revolutions of fluid machines of the type in question they are subjected to very high stresses which quite rapidly lead to material fatigue. This is particularly disadvantageous if such fluid machines are used in pneumatically operated hand tools because the motors are small and consequently the springs also must be small, and it is particularly disadvantageous if such a motor is of the type wherein the outer component is the one that rotates and wherein the reliable sealing contact of the vanes relies exclusively upon the proper operation of the springs.